Sources of unintentionally produced polychlorinated naphthalenes

Assessment of polychlorinated naphthalenes in Korean foods: Levels, profiles, and dietary intake

Concerns about dioxin-like compounds have increased; however, the monitoring of polychlorinated naphthalenes (PCNs) in food and the assessment of dietary intake remain limited. In this study, various foods were collected from Korean markets and analyzed for PCNs. Fishery products exhibited the highest mean concentration (48.0 pg/g ww) and toxic equivalent (TEQ) (0.0185 pg-TEQ/g ww). Agricultural products were the largest contributors (35.7%) to the total dietary intake of PCNTEQ, followed by livestock products (33.6%), fishery products (20.2%), and processed foods (10.5%). The mean intake of PCNTEQ for the Korean population was 0.901 pg-TEQ/day for males and 0.601 pg-TEQ/day for females. Generally, males and younger groups had higher daily intakes of PCNTEQ, but they did not exceed the tolerable weekly intakes. Nonetheless, it is important to manage potential health risks associated with PCNs and other dioxin-like compounds by identifying major food items contributing to PCN exposure and considering age and gender differences.

Scientometric trends and knowledge maps of global polychlorinated naphthalenes research over the past four decades

Polychlorinated naphthalenes (PCNs) were included in the banned list of the Stockholm Convention due to their potential to provoke a wide range of adverse effects on living organisms and the environment. Many reviews have been written to clarify the state of knowledge and identify the research needs of this pollutant class. However, studies have yet to analyse the scientometric complexities of PCN literature. In this study, we used bibliometric R and vosviewer programs as a scientometric tool to fill this gap by focusing on articles indexed on Web of Science and Scopus databases and those published between 1973 and 2022. A total of 707 articles were published within this period with a publication/author, author/publication, and co-authors/publication ratios of 0.45, 2.19, and 4.86, respectively. Developed countries dominated most scientometric indices (number of publications, citations, and collaboration networks) in the survey period. Lotka's inverse square rule of author productivity showed that Lotka's laws do not fit PCN literature. An annual percentage growth rate of 7.46% and a Kolmogorov-Smirnoff goodness-of-fit of 0.88 suggests that more output on PCNs is likely in years to come. More research is needed from scholars from developing countries to measure the supremacy of the developed nations and to effectively comply with the Stockholm Convention agreement.

Atmospheric emissions of hexachlorobutadiene in fine particulate matter from industrial sources

Hexachlorobutadiene (HCBD) is a concerning chemical that is included in the United States Toxic Substances Control Act, and the Stockholm Convention. Knowledge of the sources of HCBD is insufficient and is pivotal for accurate inventory and implementing global action. In this study, unintentional HCBD release and source emission factors of 121 full-scale industrial plants from 12 industries are investigated. Secondary copper smelting, electric arc furnace steelmaking, and hazardous waste incineration show potential for large emission reductions, which are found of high HCBD emission concentrations of > 20 ng/g in fine particulate matter in this study. The highest HCBD emission concentration is observed for the secondary copper smelting industry (average: 1380 ng/g). Source emission factors of HCBD for the 12 industries range from 0.008 kg/t for coal fire power plants to 0.680 kg/t for secondary lead smelting, from which an estimation of approximately 8452.8 g HCBD emissions annually worldwide achieved. The carcinogenic risks caused by HCBD emissions from countries and regions with intensive 12 industrial sources are 1.0-80 times higher than that without these industries. These results will be useful for formulating effective strategies of HCBD control.

Accurate Experimental Structure of 1-Chloronaphthalene

The structure of isolated 1-chloronaphthalene has been investigated in a supersonic expansion by high-resolution chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy in the 2-8 GHz frequency range. Accurate values of the rotational, centrifugal distortion, and nuclear quadrupole coupling constants for the only availabe conformer have been determined. The intensity of the spectrum allowed us to observe all the heavy atoms isotopologues in natural abundance, determining their rotational constants. From the extensive experimental dataset we derived accurate structures for 1-chloronaphthalene using different methodologies and compared with related compounds.

Polychlorinated naphthalenes in freshwater fish from Beijing markets: Species-specific differences, effects of cooking, and health risk assessment

Fish are an important source of human dietary exposure to polychlorinated naphthalenes (PCNs). The occurrence and sources of PCNs in different species of freshwater fish are unknown, and few studies have assessed human exposure risks to PCNs through freshwater fish. In this study, 140 freshwater fish samples from 10 species were collected from Beijing markets, China. The Σ75CNs concentration range in the fish was 20.7-1310 pg/g wet weight (ww). The highest median Σ75PCNs concentration (80.4 pg/g ww) was found in mandarin fish (Siniperca chuatsi), and the lowest (29.6 pg/g ww) in snakehead (Channa argus). Di- and tri-CNs were the dominant PCN homologues with contributions of 35.3 % and 30.8 %, respectively. Unintentionally produced PCNs from metal smelting might be the source of PCN contamination in freshwater fish. The cooking temperature and time did not significantly affect the PCN concentrations in fish or the PCN homologue profiles. The highest toxic equivalent (TEQ) value was observed in sturgeon (Acipenser sinensis), followed by mandarin fish. Hexa-CNs were the most abundant homologue for the PCN TEQs. A risk assessment indicated that the dietary exposure risks for local residents to PCNs through freshwater fish were low. However, the relatively high concentrations of PCNs in the samples deserve attention to avoid PCNs exposure risks for groups with high fish consumption rates. Furthermore, freshwater fish likely contain a mixture of contaminants including dioxin and furans which also display a similar mode of toxicity as the PCNs and could enhance the risk to fish consumers.

The long-term spatial and temporal distributions of polychlorinated naphthalene air concentrations in Fildes Peninsula, West Antarctica

The knowledge of polychlorinated naphthalenes (PCNs) in the Antarctic atmosphere is quite limited compared to the Arctic. PCNs are a global concern because of their PBT characteristics (i.e., persistent, bioaccumulative, and toxic) and severe and often deadly biological effects on people and other animals. Therefore, the present study used a passive air sampling method to conduct long-term air monitoring of PCNs for almost a decade from 2013 to 2022, specifically on Fildes Peninsula, situated on King George Island, located in West Antarctica. The median sum of mono-CNs to octa-CN concentration (∑75PCNs) in the Antarctic atmosphere was 12.4 pg/m3. In terms of homologues, mono-CNs to tri-CNs predominated. Among these, the prevalent congeners observed were PCN-1 and PCN-2, originating from mono-CNs, followed by PCN-5/7 from di-CNs, and PCN-24/14 from tri-CNs, respectively. Between 2013 and 2022, the total levels of PCNs were found to have decreased approximately fourfold. Ratio analyses and principal component analysis (PCA) showed that the long-range atmospheric transport and combustion-related sources as the potential PCN sources in the study area. This paper provides the most up-to-date temporal trend analysis of PCNs in the Antarctic continent and is the first to document all 75 congeners (mono-CNs to octa-CN homologue groups).

Target Analysis of Polychlorinated Naphthalenes and Nontarget Screening of Organic Chemicals in Bovine Milk, Infant Formula, and Adult Milk Powder by High-Resolution Mass Spectrometry

Infant formula is intended as an effective substitute for breast milk but is the main source of polychlorinated naphthalenes (PCNs) to nonbreastfed infants. We performed target and nontarget analyses to determine PCNs and identify other organic contaminants in infant formula. The mean PCN concentrations in infant formula, milk powder, and bovine milk were 106.1, 88.8, and 78.2 μg kg-1 of dry weight, respectively. The PCN congener profiles indicated that thermal processes and raw materials were probably the main sources of PCNs in infant formula. A health risk assessment indicated that PCNs in infant formula do not pose health risks to infants. Using gas chromatography-Orbitrap mass spectrometry, 352, 372, and 161 organic chemicals were identified in the infant formula, milk powder, and bovine milk samples, respectively. Phthalate esters were detected in all four plastic-packed milk powder samples. The results indicated milk becomes more contaminated with organic chemicals during manufacturing, processing, and packaging.

An updated global overview of the manufacture and unintentional formation of polychlorinated naphthalenes (PCNs)

This review updates information on the historical manufacture and unintentional production of polychlorinated naphthalenes (PCNs). The direct toxicity of PCNs as a result of occupational human exposure and through contaminated feed in livestock was recognised decades ago, making PCNs a precursor chemical for consideration in occupational medicine and occupational safety. This was confirmed by the listing of PCNs by the Stockholm Convention as a persistent organic pollutant in the environment, food, animals and humans. PCNs were manufactured globally between 1910 ∼ 1980, but reliable data on the volumes produced or national outputs are scarce. A total figure for global production would be useful for the purposes of inventory and control and it is clear that combustion related sources such as waste incineration, industrial metallurgy and use of chlorine are current major sources of PCNs to the environment. The upper bound estimate of total global production has been put at 400,000 metric tons but the amounts (at least, many 10 s of tonnes) that are currently emitted unintentionally every year through industrial combustion processes should also be inventoried along with estimates for emissions from bush and forest fires. This would however require considerable national effort, financing and co-operation from source operators. The historical (1910-1970 s) production and resulting emissions through diffusive/evaporative releases through usage, are still reflected in documented occurrence and patterns of PCNs in human milk in Europe and other locations worldwide. More recently, PCN occurrence in human milk from Chinese provinces has been linked to local unintentional emissions from thermal processes.

Spatial and temporal trends of polychlorinated naphthalenes in the Arctic atmosphere at Ny-Ålesund and London Island, Svalbard

Polychlorinated naphthalenes (PCNs) are ubiquitous atmospheric pollutants that can even be found in the most remote region of the Arctic. However, temporal trend analysis and reports on mono- to octa-CN in the Arctic air are still scarce. In the present study, 8 years of atmospheric monitoring data of PCNs on Svalbard was investigated using XAD-2 resin passive air samplers (PASs) from 2011-2019. The concentrations of ∑₇₅ PCNs in the Arctic air ranged from 4.56 to 85.2 pg/m³, with a mean of 23.5 pg/m³. The mono-CNs and di-CNs were the dominant homologue groups accounting for 80 % of the total concentrations. The most abundant congeners were PCN-1, PCN-2, PCN-24/14, PCN-5/7, and PCN-3, respectively. A declining time trend of PCN concentration was observed from 2013 to 2019. The reduction in PCN concentrations is likely due to declining global emissions and banned production. However, no significant spatial difference was observed among the sampling sites. The total PCN toxic equivalency (TEQ) concentrations in the Arctic atmosphere ranged from 0.043 to 1.93 fg TEQ/m³ (mean 0.41 fg TEQ/m³). The fraction of combustion-related congeners to ∑PCNs (tri- to octa-CN) analysis results indicated that the sources of PCNs in the Arctic air were contributed mainly from reemissions of historical Halowax mixtures and combustion-related sources. To the best of our knowledge, this is the first research to report all 75 PCN congeners and homologue groups in Arctic air. Therefore, this study provides data on recent temporal trend analysis as well as all the 75 PCN congeners in the Arctic atmosphere.

Polychlorinated naphthalenes in milk-based infant and toddler formula sold on the Chinese market

Polychlorinated naphthalenes (PCNs) are dioxin-like compounds that have been reported to be present in a wide variety of foodstuffs. Milk-based infant and toddler formula sometimes plays an important role in the diet of young children and could potentially cause adverse effects if contaminated with PCNs. This study investigated the concentrations of PCNs in commercial milk-based formula produced in different countries and sold on the Chinese market for three age groups: 0-6, 6-12 and 12-36 months. The total concentrations of PCNs in 72 samples from different countries of formula based on cow milk ranged from 7.8 to 30.3 pg/g whole weight (ww). Although the PCN concentrations in formula produced in Asia, Europe and South Pacific varied, all had comparable toxic equivalent (TEQ) values. Tri-CNs were the predominant PCN homologue in all samples. No significant differences in the concentrations of PCNs were found between samples of formula for each of the three age groups. The mean TEQ for PCNs in goat milk formula samples (0.0031 pg TEQ/g ww) was higher than the value for cow milk formula (0.0009 pg TEQ/g ww) produced in China, and the proportion of higher chlorinated PCNs in goat milk formula was also higher. Based on dry weight, the mean concentration of PCNs in the raw cow milk (119 pg/g dry weight (dw)) used to produce infant and toddler formula was higher than that in the actual formula (24.2 pg/g dw), and the PCN profiles also varied between the raw milk and formula. A risk assessment indicated that, in China, consuming formula poses a lower risk to infants and toddlers from based on exposure to PCNs compared with consuming breast milk.

Computational modeling of aquatic toxicity of polychlorinated naphthalenes (PCNs) employing 2D-QSAR and chemical read-across

Polychlorinated naphthalenes (PCNs) are produced from a variety of industrial sources, and they reach the aquatic ecosystems by the dry-wet deposition from the atmosphere and also by the drainage from the land surfaces. Then the PCNs can be transmitted through the food chain to humans and show toxic effects on different aquatic animals as well as humans. Considering this scenario, it is an obligatory task to explore the toxicity data of PCNs more deeply for the species of an aquatic ecosystem (green algae-Daphnia magna-fish), and to extrapolate those data for humans. But the toxicity data for different aquatic species are quite limited. The laboratory experimentations are complicated and ethically troublesome to fill toxicity data gaps; therefore, different in silico methods (e.g., QSAR, quantitative read-across predictions) are emerging as crucial ways to fill the data gaps and hazard assessments. In the present study, we developed individual toxicity models as well as interspecies models from the 75 PCN toxicity data against three aquatic species (green algae-Daphnia magna-fish) by employing easily interpretable 2D descriptors; these models were validated rigorously employing different globally accepted internal and external validation metrics. Then we interpreted the modelled descriptors mechanistically with the endpoint values for better understanding. And finally, we endeavored to improve the prediction quality in terms of external validation metrics by employing a novel quantitative read-across approach by pooling the descriptors from the developed individual QSAR models.

Distributions of polychlorinated naphthalenes in beef from China and associated health risks

Polychlorinated naphthalenes (PCNs) are toxic and can accumulate through the food chain. PCNs have been detected in different categories of foods. Intake of animal-derived foods is an important pathway for human exposure to PCNs. However, information on PCNs in meat from farmed animals is scarce. In this study, PCNs were assessed in beef sourced from local markets in Beijing and six provinces in China. The mean PCN concentrations in beef samples from the seven regions varied from 41.2 to 88.7 pg/g wet weight (ww). The homologue profiles of PCNs in the specimens were similar, with tri- and di-CNs being dominant. The mean concentration of PCNs in the flank (74.7 pg/g ww) was higher than that in the round (58.2 pg/g ww) or shank (53.6 pg/g ww), likely because the former contained a higher proportion of lipids than the latter. Significantly different PCN distributions in beef and dairy cow milk were identified using machine learning. The toxic equivalencies (TEQs) of PCNs in all beef samples ranged from 0.0003 to 0.022 pg TEQ/g ww. PCNs contributed to approximately 4.6% of the total TEQ values of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and PCNs in the beef. Health risks related to the intake of PCNs through beef consumption by the average person living in China were minimal.

PCBs, PCNs, and PCDD/Fs in Soil around an Industrial Park in Northwest China: Levels, Source Apportionment, and Human Health Risk

The concentrations of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soil samples collected around an industrial park in Northwest China, to investigate the potential impacts of park emissions on the surrounding environment. The total concentration ranges of PCBs, PCNs, and PCDD/Fs in the soil samples were in 13.2-1240, 141-832, and 3.60-156 pg/g, respectively. The spatial distribution and congener patterns of PCBs, PCNs, and PCCD/Fs indicated that there might be multiple contamination sources in the study area, so source apportionments of PCBs, PCNs, and PCCD/Fs were performed by a positive matrix factorization model based on the concentrations of all target congeners together. The results revealed that these highly chlorinated congeners (CB-209, CN-75, and OCDF) might be derived from phthalocyanine pigments, the legacy of Halowax 1051 and 2,4-D products, which together contributed nearly half of the total concentration of target compounds (44.5%). In addition to highly chlorinated congeners, the local industrial thermal processes were mainly responsible for the contamination of PCBs, PCNs, and PCDD/Fs in the surrounding soil. The total carcinogenic risk of PCBs, PCNs, and PCDD/Fs in a few soil samples (0.22 × 10-6, 0.32 × 10-6, and 0.40 × 10-6) approached the threshold of potential carcinogenic risk (1.0 × 10-6). Since these pollutants can continuously accumulate in the soil, the contamination of PCBs, PCNs, and PCDD/Fs in surrounding soil deserves continuous attention.

Pilot study on the effect of secondary copper smelters on polychlorinated naphthalene contamination in surrounding agricultural areas

Polychlorinated naphthalenes (PCNs) are dioxin-like persistent organic pollutants that are primarily produced unintentionally during industrial thermal processes. These compounds are harmful to the environment and human health. This study investigated the occurrences of all 75 PCN congeners in agricultural areas near secondary copper smelters in China. The PCN concentrations in aquatic foods, eggs, crops, sediments and soils within 10 km of these smelters were higher than those in samples collected 20-30 km away from such facilities. In contrast, the PCN concentrations in compound animal feed samples collected at different distances from the secondary copper smelters were comparable to one another. Similar PCN homologue patterns were found in crop, egg, feed and soil samples collected at different distances from the smelters but the homologue profiles of PCNs in aquatic food and sediment samples collected from different distances varied. Lower chlorinated naphthalenes were the predominant homologues in most samples. The contamination of farm animals and crops with PCNs might result from the emission of these compounds from such sources into the surrounding environment. However, the health risks associated with human exposure to PCNs through food consumption are low for both distances (<10 km and 20-30 km) from secondary copper smelters.

Health risk assessment to polychlorinated naphthalenes dioxin-like compounds in French sea food consumers

There has been a recent revival of interest in some historical contaminants such as polychlorinated naphthalenes (PCNs). However, occurrence data are still lacking in some countries although industrial production of PCNs has been reported. This observation led to the first ever assessment of their presence in fish and seafood products in France in the present work. Their analysis was integrated in an already validated method applied for polychlorinated dibenzodioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs), based on the structural similarity existing between these POPs. Performances of the method (LODs in the range 0.10-0.28 pg g^-1 wet weight (ww), LOQs in the range 0.33-0.93 pg g^-1 ww), enabled monitoring 69 di-to octachlorinated congeners in a large representative set of fish and seafood samples collected in 2005 in four coastal areas of the French mainland (n > 30). Their systematic presence was demonstrated in all the investigated seafood products, with levels (ΣPCNs in the range 2-440 pg g^-1 wet weight) close to those already reported in other European fish and seafood sampled at a similar period. In addition, the robust measurement of almost all possible PCNs (69/75) allowed a fine interpretation of the observed profiles, highlighting in particular the specificities between species and fishing areas. Compared to the PCDD/Fs, PCBs, and polybrominated diphenylethers levels also measured for this set of samples, PCNs were observed as minor contributors to total concentrations (0.05-3.2%). The specific PCN related dietary dioxin-like exposure could be evaluated at 0.028-0.051 pg of toxic equivalent (TEQ) per kg of body weight per week for an adult, based on fish and seafood consumption only. Overall, this study provides the first baseline data on the occurrence of a large number of PCNs in France, which will allow future evaluation of temporal trends and associated risks.

Distribution and source identification of polychlorinated naphthalenes in bees, bee pollen, and wax from China

Polychlorinated naphthalenes (PCNs) are highly toxic and persistent organic pollutants that can cause adverse effects in the environment and on human health. PCNs have been detected in remote areas because of their long-range transportation. Bees and bee products are commonly used as biomonitors for various pollutants in the environment. However, information on PCNs in apiaries is scarce. The aim of this study was to evaluate the occurrences of PCNs in bees and bee products from apiaries located in different geographical regions of China, and to identify potential pollution sources and assess exposure risks to humans. Our results showed that the average Σ₇₅PCNs concentrations in bees, pollen, and wax were 74.1, 96.3, and 141 pg/g dry weight, respectively. The homologue and congener profiles of PCNs in bees, pollen, and wax were similar, and di- and tri-chlorinated naphthalenes (>60%) were the predominant homologues. The concentrations and distributions of PCNs in bees, pollen, and wax varied among different geographical regions, but their occurrences were correlated with PCN metallurgical sources in China. The health risks of PCNs in pollen were evaluated, and both carcinogenic and non-carcinogenic risks of PCNs exposure to humans through the diet were low.

Occurrence of polychlorinated naphthalenes in dairy cow farms in proximity to an iron smelting plant in China: A preliminary study

Animal derived foods are the primary pathway for human exposure to polychlorinated naphthalenes (PCNs), and various foodstuffs have been reported to contain PCNs. However, information on how PCN emission sources affect surrounding animal farms is scarce. The present study determined PCN levels in cow's milk, excrement, feed, plant and soil samples collected from four dairy farms situated within 10 km of an iron smelting plant in China. PCN concentrations in the milk samples from all four farms were in the range from 470 to 797 pg/g lipid weight while the PCN concentrations in the other specimens decreased in the order: plant > soil > excrement > feed. Higher PCN concentrations appeared in silage than in other feedstuffs, and the relationships between PCNs in milk, excrement and feed were closer than those in plant and soil. Human exposure risk to PCNs by consuming milk from this region was relatively higher than in less polluted areas.

Concentration and risk assessment of PCNs in green tea in different locations in China

Polychlorinated naphthalenes (PCNs) were added to the Stockholm Convention list of persistent organic pollutants in 2015. PCNs are mainly unintentionally produced during industrial processes nowadays, and can be widely found in environmental media and foodstuffs. Dietary intake is the primary pathway for human exposure to PCNs. PCNs in different categories of foodstuffs have been reported. However, little information on PCN concentrations in green tea, a popular beverage worldwide is available. In this study, all 75 PCN congener concentrations and distributions in green tea samples (n = 102) from 11 regions in China were determined, and risk assessment of human exposure to PCNs through tea consumption was conducted. The PCN concentrations in all the green tea samples were 3.62-175 pg/g dry weight (mean 36.1 pg/g dry weight). Similar PCN homolog and congener profiles were found in green tea samples from different areas. The dominant PCN homologs in all of the green tea samples were di-CNs, tetra-CNs, and tri-CNs. No direct relationships were found between PCN emission sources and PCN concentrations in the green tea samples. The brewing technique could affect the PCN concentrations and homolog profiles in tea leaves. PCNs in green tea from China were found to pose little risk to humans.

PCNs, PCBs, and PCDD/Fs in Soil around a Cement Kiln Co-Processing Municipal Wastes in Northwestern China: Levels, Distribution, and Potential Human Health Risks

To evaluate the impact of the first cement kiln co-processing municipal wastes in northwest China on the surrounding environment, the concentrations of polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in 17 soil samples collected around the plant. The concentration ranges of PCNs, PCBs, and PCDD/Fs were 132-1288, 10.8-59.5, and 2.50-5.95 pg/g, and the ranges of toxic equivalents (TEQ) were 1.98-20.8, 2.36-48.0, and 73.2-418 fg/g, respectively. The concentrations of PCNs, PCBs, and PCDD/Fs in this study were generally lower than those in soil around municipal waste incinerators and industrial parks in other areas. An exponential function equation was applied for the relationship between the concentration of the target compounds and the distance from the cement kiln stack, the results showed that PCN and PCB concentrations declined with the increasing of distance from the stack. Furthermore, it was found that the effect of the cement kiln on surrounding soil contaminations with PCNs and PCBs was stronger than that of PCDD/Fs by comparing the PCN, PCB, and PCDD/F homologue profiles in the fly ash sample from the plant and soil samples at different distances. The total carcinogenic risks (CR) of PCNs, PCBs, and PCDD/Fs for children and adults in soil were 1.65 × 10^-8-8.93 × 10^-8 and 1.70 × 10^-8-9.16 × 10^-8, respectively, which was less than the risk threshold (CR = 1 × 10^-6), and there was no health risk.

Contamination and sources of polychlorinated naphthalenes in the surface sediments of Chaobai River, China

In aquatic systems, sediment is both a sink for persistent organic pollutants (POPs) and a potential source of POPs release. Consequently, it is important to understand the pollution characteristics and sources of polychlorinated naphthalenes (PCNs) as POPs of Stockholm Convention in sediment for control of the ecological risk. Atmospheric deposition is a potential source of PCNs in sediment. However, there is no clear report on the contribution of atmospheric deposition to PCNs in sediments. In this study, the Chaobai River in China was selected because it is an important drinking water source that is not affected by wastewater discharge. Surface sediments from the river were analyzed for 75 PCN congeners by using high resolution gas chromatography combined with high resolution mass spectrometry. The total PCNs concentration ranged from 54 to 2266 (mean: 402) pg/g. The toxic equivalent quantity of 19 PCNs in surface sediments was 9.69 × 10^-2, and CN73, CN66/CN67, and CN63 had the largest contributions to this value. Dichlorinated and trichlorinated naphthalenes were the dominant homologs. The PCN data from the sediment samples in this study were combined with data for PCNs in ambient air from a literature, which has a good match with this study in both temporal and spatial scales. The contribution of atmospheric deposition to PCNs in the surface sediment was evaluated by comparing congener characteristics and correlation analysis. Our study indicated atmospheric transportation and deposition are important pathways for transport of PCNs into surface sediments.

The toxicological profile of polychlorinated naphthalenes (PCNs)

The legacy of polychlorinated naphthalenes (PCNs) manufactured during the last century continues to persist in the environment, food and humans. Metrological advances have improved characterisation of these occurrences, enabling studies on the effects of exposure to focus on congener groups and individual PCNs. Liver and adipose tissue show the highest retention but significant levels of PCNs are also retained by the brain and nervous system. Molecular configuration appears to influence tissue disposition as well as retention, favouring the higher chlorinated (≥ four chlorines) PCNs while most lower chlorinated molecules readily undergo hydroxylation and excretion through the renal system. Exposure to PCNs reportedly provokes a wide spectrum of adverse effects that range from hepatotoxicity, neurotoxicity and immune response suppression along with endocrine disruption leading to reproductive disorders and embryotoxicity. A number of PCNs, particularly hexachloronaphthalene congeners, elicit AhR mediated responses that are similar to, and occur within similar potency ranges as most dioxin-like polychlorinated biphenyls (PCBs) and some chlorinated dibenzo-p-dioxins and furans (PCDD/Fs), suggesting a relationship based on molecular size and configuration between these contaminants. Most toxicological responses generally appear to be associated with higher chlorinated PCNs. The most profound effects such as serious and sometimes fatal liver disease, chloracne, and wasting syndrome resulted either from earlier episodes of occupational exposure in humans or from acute experimental dosing of animals at levels that reflected these exposures. However, since the restriction of manufacture and controls on inadvertent production (during combustion processes), the principal route of human and animal exposure is likely to be dietary intake. Therefore, further investigations should include the effects of chronic lower level intake of higher chlorinated PCN congeners that persist in the human diet and subsequently in human and animal tissues. PCNs in the diet should be evaluated cumulatively with other similarly occurring dioxin-like contaminants.

A pilot evaluation on the toxicokinetics and bioaccumulation of polychlorinated naphthalenes in laying hens

Knowledge of the transfer features of polychlorinated naphthalenes (PCNs), a class of emerging persistent organic pollutants (POPs), is still lacking concerning the environment-feed-food transfer chain of farm animals. We conducted a controlled feeding experiment with laying hens fed fly ash-contaminated diets to investigate the toxicokinetics and bioaccumulation of PCNs (tri- to octa-CNs) in the hen eggs and tissues. The eggs showed increasing PCNs levels after 14 days of oral exposure, which gradually decreased during the 28-day depuration period but still exceeded the initial levels. The apparent one-compartment half-life of ∑₆₃PCNs in the eggs was 28.9 days, which was comparable to those of other dioxin-like compounds. The uptake and depuration rates of PCN congeners in the eggs were 0.002-0.010 and 0.016-0.079 days^-1 in eggs, respectively. The depuration rates were decreased with the n-octanol/water partition coefficients (logK_OW), indicating that the eggs retained more lipophilic congeners, whereas the uptake rates increased with the logK_OW, indicating the faster deposition of the more lipophilic PCNs in eggs during the exposure period. The transfer rates of PCN congeners ranged from 0.27%-23.0%, indicating the transfer potential of PCNs from feed to eggs. Additionally, the PCN distribution in the laying hens at the end of the exposure showed tissue-specific accumulation, with the high levels of PCNs in the liver, spleen, and ovum. Positive correlations between the transfer factors (C_tissue/C_feed) and the logK_OW suggested that more lipophilic PCN congeners tended to accumulate in the tissues. After quantitatively assessing the feed-to-food transfer of PCNs in laying hens, our results highlight the risk of exposure to PCNs in the food supply chain.

Discovery of significant atmospheric emission of halogenated polycyclic aromatic hydrocarbons from secondary zinc smelting

Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are emerging persistent organic pollutants. Current knowledge on the emissions of Cl/Br- PAHs is far insufficient for source control, much less on their formation mechanisms. In this field study, Cl/Br-PAHs formation mechanisms were proposed from the macro perspective of practical secondary metal smelting industries. We found secondary zinc smelting as a significant source of Cl/Br-PAHs (9553 ng/m³ in stack gas), exceeding concentrations from other metal smelting sources by 1-2 orders of magnitude. Cl/Br-PAH emission characteristics differed between various secondary metal smelting processes, indicating dominance of different formation mechanisms. Cl/Br-PAHs with fewer rings were dominant from secondary zinc smelting and secondary copper smelting. Differently, emissions from secondary aluminum smelting were dominated by congeners with more rings. The differences in congener profiles were attributable to the catalytic effects of metal compounds during smelting activities. Zinc oxide and copper oxide dominantly catalyzed dehydrogenation reactions, contributing to the formation of intermediate radicals and subsequent dimerization to Cl/Br-PAHs with fewer rings. Differently, aluminum oxide induced alkylation reactions and accelerated ring growth, resulting in the formation of Cl-PAHs with more rings. The newly proposed mechanisms can successfully explain the emission characteristics of Cl/Br-PAHs during smelting activities, which should be important implication for Cl/Br-PAHs targeted source control.

Polychlorinated naphthalenes in farmed Chinese mitten crabs in China: Concentration, distribution and source analysis

Polychlorinated naphthalenes (PCNs) are both highly toxic and bioaccumulative environmental contaminates. Dietary intake is the primary pathway for human exposure to PCNs, and PCN concentrations in aquatic foodstuffs are relatively high. Chinese mitten crab (Eriocheir sinensis) is one kind of popular aquatic foodstuffs in Asian countries. Farmed crabs could exposure to PCNs both through feed and environment. However, information on the occurrence of PCNs in farmed crabs is scarce. The present study investigated 75 PCN congeners in farmed Chinese mitten crabs, crab compound feed and sediments collected from Anhui Province and Shanghai in China. The total PCN concentrations in farmed Chinese mitten crabs from Anhui Province and Shanghai were 11.2-42.2 and 5.46-43.8 pg/g wet weight (ww), respectively. The PCN homologue profiles in crabs from both areas were similar, and both were dominated by di-CNs and penta-CNs. In contrast, lower chlorinated PCNs (di-CNs, tri-CNs and tetra-CNs) were the most common homologues in specimens of crab compound feed and sediment samples, indicating that selective bioaccumulation and metabolism of PCNs might occur in farmed crabs. No regional differences were found in the PCN congener profiles of farmed crabs, feed and sediment samples taken from Anhui Province and Shanghai. An assessment found no significant health risk associated with Chinese exposure to PCNs through farmed Chinese mitten crab consumption.

Congener profiles and process distributions of polychlorinated biphenyls, polychlorinated naphthalenes and chlorinated polycyclic aromatic hydrocarbons from secondary copper smelting

Secondary copper smelting is an important industrial source of unintentionally produced persistent organic pollutants (UPOPs) emissions. Herein, field study on industrial-scale plants was conducted to clarify the levels and profiles of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and chlorinated polycyclic aromatic hydrocarbons (> 3 rings, Cl-PAHs) from secondary copper smelting plants. The three UPOPs emission levels from the oxygen-enriched smelting furnace were higher than that from the anode furnace, which was attributed to the low-grade raw materials used. The toxic equivalent quantity concentrations of Cl-PAHs were 1.3-4.4 and 4.6-18.9 times higher than that of PCBs and PCNs, respectively. Thus, the emission control of Cl-PAHs in the secondary copper industry should be of concern. The chlorination degree of PCBs and PCNs was ~4 after the gas-cooling stage but was reduced to 1-2 in the stack outlet. This result indicated that the PCBs and PCNs congeners that were generated during the cooling stage were mainly higher-chlorinated. After purification by air pollution control devices (APCDs), the high-chlorinated congeners were removed simultaneously with the fly ash, whereas the low-chlorinated congeners may be regenerated and transferred into the stack gas due to possible memory effect within the APCDs.

Occurrence and source analysis of polychlorinated naphthalenes in raw cow milk

The potential contamination of food items with polychlorinated naphthalenes (PCNs) has attracted increasing attention because of their toxicity, persistence and bioaccumulative characteristics. Humans are exposed to PCNs primarily through consuming animal-derived foodstuffs. However, the pathways by which PCNs can enter the food supplying chain are poorly understood. In this study, Σ₇₅PCNs were determined in raw cow milk (n = 82) collected from three different regions that varied in the intensity of PCNs emission sources in North China, using high-resolution gas chromatography/high-resolution mass spectrometry method. Higher PCN concentrations (214-2050 pg/g lw) were found in raw cow milk from dairy cow farms located in the region with relatively higher intensity of emission sources. Less chlorinated congeners were dominant in all raw cow milk samples. PCNs in cow milk might result from industrial fly ash emissions that contaminate animal feed through atmospheric deposition. Risks posed to humans through consuming PCNs in cow milk were low.

Contamination characteristics of polychlorinated naphthalenes in the agricultural soil of two industrial cities in South Korea

This study investigates the contamination characteristics of polychlorinated naphthalenes (PCNs) in the rice paddy soils of two industrial cities (Pohang and Ulsan) in South Korea. The paddy soils were collected from 40 sites in the paddy fields near industrial complexes in both cities. The mean concentration of Σ₅₅ PCNs was 145.9 ± 101.7 pg/g and 95.4 ± 41.4 pg/g for the soils in Pohang and Ulsan, respectively. The toxic equivalents (TEQs) of Σ₂₈ PCNs ranged from 0.007 pg-TEQ/g to 0.069 pg-TEQ/g in Pohang, and 0.015 pg-TEQ/g to 0.046 pg-TEQ/g in Ulsan. The PCN profiles were dominated by lower chlorinated homologues such as tetra- and tri-CNs for both cities, which are associated with the historical use of technical products, or more specifically, Halowaxes (HW 1099, 1031, 1013, and 1001). The results of the principal component analysis (PCA) indicate that the historical residues from the technical products contributed to the PCN contamination, but the influence of combustion sources was also observed with a high fraction of combustion-related congeners. Based on this study, we can expect that rice grown in these paddy fields will accumulate PCNs and other combustion-related pollutants, strongly suggesting the necessity for multimedia (e.g., air, soil, water, and rice) monitoring and human exposure assessments of PCNs.

Using Polychlorinated Naphthalene Concentrations in the Soil from a Southeast China E-Waste Recycling Area in a Novel Screening-Level Multipathway Human Cancer Risk Assessment

Polychlorinated naphthalene (PCN) concentrations in the soil at an e-waste recycling area in Guiyu, China, were measured and the associated human cancer risk due to e-waste-related exposures was investigated. We quantified PCNs in the agricultural soil and used these concentrations with predictive equations to calculate theoretical concentrations in outdoor air. We then calculated theoretical concentrations in indoor air using an attenuation factor and in the local diet using previously published models for contaminant uptake in plants and fruits. Potential human cancer risks of PCNs were assessed for multiple exposure pathways, including soil ingestion, inhalation, dermal contact, and dietary ingestion. Our calculations indicated that local residents had a high cancer risk from exposure to PCNs and that the diet was the primary pathway of PCN exposure, followed by dermal contact as the secondary pathway. We next repeated the risk assessment using concentrations for other carcinogenic contaminants reported in the literature at the same site. We found that polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and PCNs caused the highest potential cancer risks to the residents, followed by polychlorinated biphenyls (PCBs). The relative importance of different exposure pathways depended on the physicochemical properties of specific chemicals.

Formation of Environmentally Persistent Free Radicals during Thermochemical Processes and their Correlations with Unintentional Persistent Organic Pollutants

Attention is increasingly being paid to environmentally persistent free radicals (EPFRs), which are organic pollutants with the activities of free radicals and stabilities of organic pollutants. EPFRs readily form during thermal processes through the decomposition of organic precursors such as phenols, halogenated phenols, and quinone-type molecules, which are also important precursors of toxic unintentionally produced persistent organic pollutants (UPOPs). We have found that EPFRs are important intermediates for UPOP formation during thermal-related processes. However, interest in EPFRs is currently mostly focused on the toxicities and formation mechanisms of EPFRs themselves. Little information is available on the important roles EPFRs play in toxic UPOP formation during thermal processes. Here, we review the mechanisms involved in EPFR formation and transformation into UPOPs during thermal processes. The review is focused on typical EPFRs, including cyclopentadiene, phenoxy, and semiquinone radicals. The reaction temperature, metal species present, and oxygen concentration strongly affect EPFR and UPOP formation during thermal-related processes. Gaps in current knowledge and future directions for research into EPFR and UPOP formation, transformation, and control are presented. Understanding the relationships between EPFRs and UPOPs will allow synergistic control strategies to be developed for thermal-related industrial sources of EPFRs and UPOPs.

Concentrations of organic contaminants in industrial and municipal bioresources recycled in agriculture in the UK

Many types of bioresource materials are beneficially recycled in agriculture for soil improvement and as alternative bedding materials for livestock, but they also potentially transfer contaminants into plant and animal foods. Representative types of industrial and municipal bioresources were selected to assess the extent of organic chemical contamination, including: (i) land applied materials: treated sewage sludge (biosolids), meat and bone meal ash (MBMA), poultry litter ash (PLA), paper sludge ash (PSA) and compost-like-output (CLO), and (ii) bedding materials: recycled waste wood (RWW), dried paper sludge (DPS), paper sludge ash (PSA) and shredded cardboard. The materials generally contained lower concentrations of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) relative to earlier reports, indicating the decline in environmental emissions of these established contaminants. However, concentrations of polycyclic aromatic hydrocarbons (PAHs) remain elevated in biosolids samples from urban catchments. Polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) were present in larger amounts in biosolids and CLO compared to their chlorinated counterparts and hence are of potentially greater significance in contemporary materials. The presence of non-ortho-polychlorinated biphenyls (PCBs) in DPS was probably due to non-legacy sources of PCBs in paper production. Flame retardent chemicals were one of the most significant and extensive groups of contaminants found in the bioresource materials. Decabromodiphenylether (deca-BDE) was the most abundant polybrominated diphenyl ether (PBDE) and may explain the formation and high concentrations of PBDD/Fs detected. Emerging flame retardant compounds, including: decabromodiphenylethane (DBDPE) and organophosphate flame retardants (OPFRs), were also detected in several of the materials. The profile of perfluoroalkyl substances (PFAS) depended on the type of waste category; perfluoroundecanoic acid (PFUnDA) was the most significant PFAS for DPS, whereas perfluorooctane sulfonate (PFOS) was dominant in biosolids and CLO. The concentrations of polychlorinated alkanes (PCAs) and di-2-ethylhexyl phthalate (DEHP) were generally much larger than the other contaminants measured, indicating that there are major anthropogenic sources of these potentially hazardous chemicals entering the environment. The study results suggest that continued vigilance is required to control emissions and sources of these contaminants to support the beneficial use of secondary bioresource materials.

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

The effect of copper and its compounds on halogenation and dehalogenation of aromatic compounds will be discussed in the proposed article. Cu oxidized to appropriate halides is an effective halogenation catalyst not only for the synthesis of halogenated benzenes or their derivatives as desired organic fine chemicals, but is also an effective catalyst for the undesirable formation of thermodynamically stable and very toxic polychlorinated and polybrominated aromatic compounds such as polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans accompanied incineration of waste contaminated with halogenated compounds or even inorganic halides. With appropriate change in reaction conditions, copper and its alloys or oxides are also able to effectively catalyze dehalogenation reactions, as will be presented in this review.

Polychlorinated Naphthalenes across the Great Lakes: Lake Trout and Walleye Concentrations, Trends, and TEQ Assessment-2004-2018

Polychlorinated naphthalenes (PCNs) were measured in lake trout and walleye over the period 2004-2018, utilizing isotope dilution techniques with high-resolution gas chromatography/high-resolution mass spectrometry to assess concentrations and toxic equivalence (TEQ). An age-trend model was applied to mitigate the effect of a changing lake trout age structure. Most Great Lakes Fish Monitoring and Surveillance Program sampling sites demonstrated significant half-life and percent decreases for lake trout total PCNs and total TEQ over the 2004-2018 period, the exceptions being Lake Erie lake trout and walleye which illustrated increasing concentrations. Great Lakes total PCN concentrations ranged between 5701 and 100 pg/g ww, whereas total PCN TEQ concentrations ranged between 8.89 and 0.13 pg-TEQ/g ww. Based on the average number of chlorines per naphthalene, we determined that the overall lake trout and walleye PCN congener distribution has significantly shifted to a lower-chlorinated composition in the Great Lakes (5.33 to 4.48 Cl/CN) and has resulted in a substantial 59.1% reduction of the overall total PCN TEQ burden. A prominent PCN concentration trend breakpoint was observed in Lake Ontario lake trout over the 2012-2016 period likely associated with hazardous waste cleanups, channel dredging, and spoils disposal in the Detroit River and western-basin of Lake Erie.

Occurrence of dioxin-like POPs in soils from urban green space in a metropolis, North China: implication to human exposure

Urban green space is a special space for urban life and natural contact and has an important impact on human health. However, little information is available on dioxin-like persistent organic pollutants (POPs) in the soils from the specific areas. We measured the concentrations of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs) in the soils from urban green space in a metropolis, North China, and found total concentrations of PCDD/Fs, PCBs, and PCNs in the range of 11.5-91.4, 14.7-444, and 82.5-848 pg/g, respectively. It was worth to notice that the concentrations of PCDD/Fs in public park soil from urban center were significantly higher than those in the road greenbelts and resident lawns (Kruskal-Wallis test, p = 0.004). The source analysis indicated that sewage sludge from wastewater treatment plants were important sources of PCNs and PCDD/Fs in urban green land soils, and atmospheric deposition from municipal solid waste incinerator (MSWI) also play an important role in PCDD/F sources. The rough exposure risk evaluation showed that the residents were at a safe level with the daily doses being 0.172-3.144 fg/kg BW/day for children and 0.022-0.406 fg/kg BW/day for adult. Due to the complex and variable sources of PCDD/Fs in urban areas, dioxin-like POPs in urban green land should be given more attention to weaken human exposure.

An assessment of the estrogenic and androgenic properties of tetra- and hexachloronaphthalene by YES/YAS in vitro assays

Many persistent organic pollutants (POPs) exhibit endocrine disrupting activity but studies on some POPs, e.g., polychlorinated naphthalenes (PCNs), are very scarce. The present study investigates the (anti)estrogenic and (anti)androgenic activities of 1,2,3,5,6,7-hexachloronaphthalane (PCN67) and 1,3,5,8-tetrachloronaphthalene (PCN43) using the yeast estrogen and androgen reporter bioassays. Among the tested substances, antiestrogenic response was only shown by PCN67. The strongest inhibition of estrogenic activity (up to 17.4%) was observed in the low concentration ranges (5 pM - 0.5 nM) in the presence of 1.5 nM 17β-estradiol. Both tested compounds showed partial estrogenic activity with a hormetic-type response. However, both studied chemicals showed strong antiandrogenic effects: their potency in the presence of 100 nM 17β-testosterone for PCN43 (IC50 = 2.59 μM) and PCN67 (IC50 = 3.14 μM) was approximately twice that of the reference antiandrogen flutamide (IC50 = 6.14 μM). It cannot be excluded that exposure to PCNs, together with other endocrine disrupting chemicals (EDCs), may contribute to the deregulation of sex steroid hormone signaling.

Concentrations and profiles of persistent organic pollutants unintentionally produced by secondary nonferrous metal smelters: Updated emission factors and diagnostic ratios for identifying sources

Secondary nonferrous metal smelters are important sources of unintentionally produced persistent organic pollutants (UPOPs) including polychlorinated biphenyls (PCBs), polychlorinated naphthalenes, pentachlorobenzene, and hexachlorobenzene. Quantifying UPOP emissions by the main sources is an important step when evaluating UPOP emissions and establishing an inventory. In this study, field investigations were performed to allow UPOP emissions and distributions in stack gases emitted by secondary nonferrous metal smelters to be compared. A total of 25 stack gas samples were collected from secondary copper smelters (SCus), secondary zinc smelters, and secondary lead smelters in China. The mean toxic equivalent concentrations (TEQs) and mass concentrations of most of the UPOPs were highest in the secondary zinc smelter stack gas samples, next highest in the SCu stack gas samples, and lowest in the secondary lead smelter stack gas samples. The mean dioxin-like PCB and polychlorinated naphthalene TEQs were ∼8.9 and ∼6.6 times higher in stack gases from a SCu equipped with an oxygen-enriched smelting furnace than in stack gases from a SCu with a converter furnace. The mean PCB-118 to PCB-123 ratios and CN-10 to CN-35 ratios varied strongly and could be used as diagnostic ratios for apportioning the sources of UPOPs in the environment. Emission factors for dioxin-like PCBs, polychlorinated naphthalenes, pentachlorobenzene, and hexachlorobenzene in stack gases from secondary nonferrous metal smelters were derived and updated. The results improve our understanding of UPOP emission and provide data for establishing UPOP emission inventories for secondary nonferrous metal smelters.

Emission characteristics of dl-PCNs, PCDD/Fs, and dl-PCBs from secondary copper metallurgical plants: Control technology and policy

This study investigated the characteristics of dl-PCNs, PCDD/Fs and dl-PCBs emitted from two typical secondary copper metallurgical plants processing copper sludge equipped with different sets of air pollution control devices (APCDs). Results indicated that the emission factors of dl-PCNs and PCDD/Fs of plant A are 0.00775 and 1.09 μg TEQ/ton, respectively, which are remarkably lower than those of plant B (3.12, 181 and 25.5 μg TEQ/ton for dl-PCNs, PCDD/Fs and dl-PCBs, respectively). Dl-PCNs contributed 0.7-2.7% of total TEQ for flue gases and up to 2.6% of TEQ for ash samples. The TEQ concentration of dl-PCNs in fly ash individually exceeds the regulated level of 1 ng TEQ/g regulated by Taiwan EPA, indicating that emission and discharge of dl-PCNs should be regulated. The combination of semidry scrubber and activated carbon injection (ACI) + baghouse (BH) is effective for simultaneous removals of dl-PCNs and PCDD/Fs in plant A; while the combination of cyclone, secondary combustion chamber, ACI + BH and wet scrubber (WS) is not optimal for removing dl-PCNs, PCDD/Fs and dl-PCBs. Memory effect occurring within BH and WS is responsible for low removal efficiencies of these POPs in plant B. This study suggests appropriate APCDs for simultaneous removal of three POP groups and recommends the inclusion of dl-PCNs in emission standard.

Reduction of polychlorinated naphthalenes (PCNs) emission from municipal waste incinerators in Taiwan: Recommendation on control technology

Emission factor and removal efficacy of PCNs are evaluated via the flue gas sampling of two MWIs equipped with different air pollution control devices (APCDs) in Taiwan. MWI-A is equipped with ESP, wet scrubber (WS) and selective catalytic reduction (SCR), while cyclone (CY), semi-dry absorber (SDA), activated carbon injection (ACI) and baghouse (BH) are employed in MWI-B. The average concentrations of PCNs measured at stacks of MWI-A and MWI-B are 2.1 ng Nm^-3 (0.218 pg TEQ Nm^-3) and 23.2 ng Nm^-3 (0.425 pg TEQ Nm^-3), respectively. The emission factors of PCNs calculated from feeding rates of waste and stack sampling results range from 6.7 to 6.95 μg t^-1 (0.790-1.45 ng TEQ t^-1). PCNs are formed in ESP via chlorination, while SCR and SDA + ACI + BH are effective in removing PCNs with the overall efficacies of 97.6% and 94.3%, respectively. PCN removal efficiencies achieved with SCR and SDA + ACI + BH increase as chlorination level increases. Specifically, around 72% and 82% of Mono-CN are removed by SCR and SDA + ACI + BH, respectively. The removal efficacies of other homologues achieved with SCR are consistently high (96-100%). Dominances of Mono-to Tri-CNs in scrubbing liquid collected from WS and higher removal efficacies of these homologues achieved with WS + ESP compared with ESP alone indicate that WS can capture low chlorinated PCNs to some extent. The results suggest that CY + SDA + ACI + BH should be equipped in MWI for effective removal of PCNs, while ESP, WS and SCR should be utilized with precaution to eliminate PCNs formation and enhance the PCNs removal efficiency.

Hexachloronaphthalene Induces Mitochondrial-Dependent Neurotoxicity via a Mechanism of Enhanced Production of Reactive Oxygen Species

Hexachloronaphthalene (PCN67) is one of the most toxic among polychlorinated naphthalenes. Despite the known high bioaccumulation and persistence of PCN67 in the environment, it is still unclear to what extent exposure to these substances may interfere with normal neuronal physiology and lead to neurotoxicity. Therefore, the primary goal of this study was to assess the effect of PCN67 in neuronal in vitro models. Neuronal death was assessed upon PCN67 treatment using differentiated PC12 cells and primary hippocampal neurons. At 72 h postexposure, cell viability assays showed an IC₅₀ value of 0.35 μg/ml and dose-dependent damage of neurites and concomitant downregulation of neurofilaments L and M. Moreover, we found that younger primary neurons (DIV4) were much more sensitive to PCN67 toxicity than mature cultures (DIV14). Our comprehensive analysis indicated that the application of PCN67 at the IC₅₀ concentration caused necrosis, which was reflected by an increase in LDH release, HMGB1 protein export to the cytosol, nuclear swelling, and loss of homeostatic control of energy balance. The blockage of mitochondrial calcium uniporter partially rescued the cell viability, loss of mitochondrial membrane potential (ΔΨ_m), and the overproduction of reactive oxygen species, suggesting that the underlying mechanism of neurotoxicity involved mitochondrial calcium accumulation. Increased lipid peroxidation as a consequence of oxidative stress was additionally seen for 0.1 μg/ml of PCN67, while this concentration did not affect ΔΨ_m and plasma membrane permeability. Our results show for the first time that neuronal mitochondria act as a target for PCN67 and indicate that exposure to this drug may result in neuron loss via mitochondrial-dependent mechanisms.

Occurrence and sources of PCBs, PCNs, and HCB in the atmosphere at a regional background site in east China: Implications for combustion sources

Multiple types of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and hexachlorobenzene (HCB), can be unintentionally released from combustion or thermal industrial processes, which are speculated to be the main sources of these contaminants, as they were banned on production and use since several decades ago. In this study, concentrations and sources of 40 PCBs, 39 PCNs, and HCB were analyzed in air samples collected during the period 2012-2015 at a background site in east China. ΣPCBs, ΣPCNs, and HCB were in the range of 9-341 pg/m³, 6-143 pg/m³, and 14-522 pg/m³, respectively. Seasonal characteristics with high levels in winter and low levels in summer were observed for PCNs and HCB. PCBs also exhibited slightly higher levels in winter. Source apportionment was conducted, using polycyclic aromatic hydrocarbons (PAHs) as combustion sources indicator, combined with principal component analysis (PCA) and positive matrix factorization (PMF) model. The results indicated that the legacy of past produced and used commercial PCBs was the dominant contributor (∼56%) to the selected PCBs in the atmosphere in east China. PCNs were mainly emitted from combustion sources (∼64%), whereas HCB almost entirely originated from combustion process (>90%).

Compositional profiles, persistency and toxicity of polychlorinated naphthalene (PCN) congeners in edible cod liver products from 1972 to 2017

Edible cod liver products including cod liver oil and canned cod liver, sampled over the last five decades from the North Atlantic region, including the Baltic Sea were analysed for a set of persistent and toxicologically significant polychlorinated naphthalene (PCN) congeners with some of the highest relative potencies (dioxin-like toxicity) among PCNs. The targeted congeners showed a near-universality of occurrence in all samples apart from the most recent sample of cod liver oil which was assumed to be highly purified, as cod livers from the same period and location showed appreciable amounts of PCNs. The majority of dominant congeners in legacy technical PCN mixtures were absent or occurred in low concentrations, raising the possibility that congeners arising from combustion related sources may be acquiring a greater significance following the decline and elimination of PCN production. The apparent appreciation in the relative amounts of PCN#70 in the last three to four decades may provide support for this view. The PCN contribution to dioxin-like toxic equivalence (TEQ) that was estimated for these samples (range 1.2-15.9 pg TEQ g^-1) was significant in comparison to the EU regulated value of 1.75 pg TEQ g^-1 for dioxins in fish oils. Most of the TEQ was associated with PCNs 66/67, 64/68, 69 and 73. Although metabolic processes are likely to influence this distribution, the profile is a little different to that observed in the tissues of higher order animals where PCNs #66/67 and #73 may contribute approximately 90% to the summed TEQ.

Concentrations, toxic equivalence, and age-corrected trends of legacy organic contaminants in Lake Champlain lake trout: 2012-2018

Our study is the first comprehensive, multi-year assessment of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs), polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans (PCDD/Fs) lake trout concentrations and trends in Lake Champlain (LC). Lake trout whole-fish, fillets, and eggs were collected over the 2012-2018 study period. Total PCB concentrations (395.7 ng/g wet weight (ww)) were the highest average concentration of any contaminant grouping reported in this study. Whole-fish lake trout modeling revealed highly significant (p < 0.05) log-linear correlations for all dioxin-like contaminants measured. Overall contaminant decreases for the 2012-2018 period ranged from 20.9% (total PCNs) to 39.3% (2378-TCDD). Contaminant decreases for total PCBs and total-5-PBDEs were 30.9% and 48.3%, respectively. Of particular significance were the measured total PBDE concentrations (74.3 ng/g ww) found in LC whole-fish lake trout. Log-linear forecasting indicates that whole-fish lake trout TEQs will be below the guidelines protective of wildlife thresholds during the periods 2035-2047 (TRG_bird) and 2062-2088 (TRG_mammal). Based on current USEPA guidelines, all lake trout fillets from Lake Champlain analyzed for this study exceed the human health cancer screening value of 0.15 pg-TEQ/g ww by a substantial margin (average = 8.61 pg-TEQ/g ww). Dioxin-like trend data collected for Lake Champlain indicates that the mechanisms of contaminant uptake, trends, and yearly percent decline reflect those found in the Great Lakes.

Characterization of PCN emission and removal from secondary copper metallurgical processes

This study investigates the characteristics of PCN emission and removal from two secondary copper metallurgical processes (plants A and B) equipped with different air pollution control devices (APCDs). Different operating conditions and feeding materials result in varying emission factors of PCNs from two plants. The average PCN concentration emitted from plant B (7597 ng Nm^-3) is significantly higher than that emitted from plant A (32.5 ng Nm^-3) and those reported in China (5.8-2845 ng Nm^-3). Similar trend is found for fly ash samples collected from two plants. Low chlorinated homologues (Mono-to Tri-CNs) are the major contributors to total PCNs measured in flue gas, fly ash and slag samples. Combination of semi-dry absorber, activated carbon injection and baghouse is effective for PCN removal in plant A, with the overall removal efficiency of 98%. The overall removal efficiency of PCNs achieved with APCDs equipped in plant B is 90%, however, increases of some homologues as the flue gases passing through baghouse and wet scrubber are found, suggesting the occurrence of memory effect within baghouse and wet scrubber.

Efficacy of the novel continuous sampling system for PCDD/Fs and unintentional persistent organic pollutants

Long-term sampling is essential for monitoring the air pollutants emitted from stack since it can monitor the pollutants emission continuously including the stages of start-up, shutdown and normal operation. However, commercial continuous sampling equipment such as AMESA faces the challenges of high weight and complicated sampling procedures. This study has developed a long-term and automatic sampling system (National Central University continuous stack sampling system, NCU-CS³), and compared the efficiency with manual sampling train (MST). The results indicate that relative standard deviation (RSD) of PCDD/Fs concentrations measured between NCU-CS³ and MST is <20%, demonstrating that the difference between NCU-CS³ and MST in measuring PCDD/Fs is insignificant. Besides, the effects of adsorbent temperature, adsorbent amount and type of adsorbent on breakthroughs of PAHs and unintentional-persistent organic pollutants (UPOPs) such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), chlorinated phenols (CPs), chlorinated benzenes (CBs) and polychlorinated naphthalenes (PCNs) are evaluated. The results indicate that the breakthrough of pollutants increases with increasing temperature of XAD-2 and decreases with increasing XAD-2 amount. Moreover, XAD-4 is used as alternative adsorbent to test the breakthrough and the results indicate that the breakthroughs of UPOPs of XAD-4 as adsorbent are lower than that with XAD-2 due to higher specific surface area of XAD-4. Furthermore, the residual of PCDD/Fs with NCU-CS³ as the sampling train is relatively low (1.5-3.8%), which meets the regulation of EN 1948-5 (10%).

Polychlorinated Naphthalene Congener Profiles in Common Vegetation on the Tibetan Plateau as Biomonitors of Their Sources and Transportation

Polychlorinated naphthalenes (PCNs) are globally transported, carcinogenic, persistent organic pollutants (POPs) that were recently added to the Stockholm Convention with 184 parties. The Tibetan Plateau plays an important role in the global transportation and distribution of POPs. Knowledge of PCN sources and transportation on the Tibetan Plateau is important for their control globally. In this study, we quantified the congener-specific concentrations of PCNs in lichen, moss, soil, and air samples collected on the Tibetan plateau and found that common lichens were effective biomonitors for predicting atmospheric PCNs in this area. The physiochemical properties of the PCNs, the temperatures, and the lichen lipid contents were identified as important factors influencing PCN partitioning between lichens and air. Lichen-air partitioning equations were established and used to predict PCN concentrations in air in Southeast Tibet. The lichens could be used as PCN biomonitors to clarify their spatial variations, sources, and transportation in the southeast of the plateau. PCN concentrations in lichens increased with altitude, suggesting that high-mountain cold-trapping influenced the PCN transportation behavior. Principal component analysis and linear discriminant analysis showed that the major source of PCNs in this region was long-range atmospheric transportation via the Indian monsoon in summer and wind from Southwest Asia in winter. This study provides a novel method using PCN congener profiles as fingerprints and statistical models for studying the geochemical effects of conditions in high-mountain regions on the contamination behaviors of 75 congeners of the notorious PCNs.

Polychlorinated naphthalenes, polychlorinated dibenzo-p-dioxins and dibenzofurans, and polychlorinated biphenyls in soils in an industrial park in Northwestern China: Levels, source apportionment, and potential human health risks

Seventeen soil samples collected in an industrial park located in Ningxia Province, Northwestern China were analyzed for polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs). The PCN, PCDD/F, and PCB concentration ranges were 183-3340, 7.00-215, and 45.1-355 pg/g, respectively. Positive matrix factorization showed that secondary ferrous metal smelters and cement kilns contributed more than 70% of the total PCN concentration. Historical use of Halowax 1051 also affected the PCN concentrations in soil. Principal component analysis indicated that the PCDD/F concentrations in soil in the study area were mainly affected by thermal processes in secondary ferrous metal smelters. CB-209 was an important contributor to total PCBs in the study area, and likely originated from the phthalocyanine-type pigments used in a local recycled paper mill. Samples S10, S1, S17, and S6 had high ∑TEQ (PCDD/Fs + PCNs + PCBs) concentrations, and the carcinogenic risks of PCDD/Fs, PCNs, and PCBs for workers from these samples were 0.487 × 10^-6, 0.234 × 10^-6, 0.230 × 10^-6, and 0.210 × 10^-6, respectively. According to our results, the health risks of PCDD/Fs, PCNs, and PCBs for workers in this area should be given more attention.

Inventory of Polychlorinated Naphthalene Emissions from Waste Incineration and Metallurgical Sources in China

Polychlorinated naphthalenes (PCNs) are highly toxic persistent organic pollutants (POPs) that are a relatively new addition to the Stockholm Convention as of 2015. The levels of unintentional emissions of PCNs from important industrial thermal sources on national scales are unclear but are important for understanding potential human exposure. In this study, an inventory was compiled of PCN emissions from priority industrial sources of unintentional POPs in China. Estimated emissions from four typical POP sources in the reference year (2014) in China were 511.6 kg by mass and 7650.8 mg of toxic equivalent. Waste incineration, secondary nonferrous smelting, electric arc furnace steelmaking, and iron ore sintering plants contributed 38.8, 15.4, 29.2, and 16.6%, respectively, to the total emissions. The Eastern Seaboard of China and the Hebei region in North China, which have intensive industrial activity and high population densities, were dominant contributors of PCNs. Only 18.6% of the counties where waste incineration plants were located emitted PCNs at a level higher than 1.00 × 10^-1 mg of toxic equivalent, whereas 80% of the counties where metallurgical plants were located emitted PCNs at this level. These results indicate effective implementation of POP control in the waste incineration industry in China. This study clarifies the unintentionally emission levels of PCNs in China and provides important information for strategy development to control source emissions.

Temporal trends in polychlorinated naphthalene emissions from sintering plants in China between 2005 and 2015

The Chinese Government has established stringent policies since 2005 to control SO₂, particulate matter, and NO_x emissions from sintering plants with the aim of tackling severe air pollution in China. Notably, sintering is also important sources of polychlorinated naphthalenes (PCNs), but it is not clear whether the air pollution control policies have led to decreased PCN emissions. In this study, the PCN concentrations in 144 stack gas, 87 discarded fly ash, and 24 desulfurization by-product samples from 24 Chinese sintering plants were determined. This study revealed that desulfurization processes decreased PCN emissions by 47.2%-72.2%. However, these PCNs were not completely eliminated, and transformed to desulfurization by-product. PCN emission in such previously ignored solid residues, including of desulfurization by-product and fine particles, produced in the process of cutting down air pollutants emissions from Chinese sintering plants between 2005 and 2015 was found contained 324 kg, and these residues therefore need to be managed better than currently. Furthermore, PCN concentrations were higher from produced in old plants than produced in new plants, so it is necessary to increase the rate at which out-of-date sintering plants are eliminated. Phasing out old sintering processes decreased total PCN emissions in China by 1549 kg between 2005 and 2015.

Polychlorinated naphthalene (PCN) emissions and characteristics during different secondary copper smelting stages

The amounts and characteristics of polychlorinated naphthalenes (PCNs) emitted by a secondary copper smelter were investigated. Differences in the amounts and characteristics of PCNs emitted during different smelting stages were investigated, and the main stage during which PCNs were emitted was identified. PCN concentrations in stack gases emitted during secondary copper smelting were 477.0-762.5 ng/m³ (4.4-8.3 pg toxic equivalents/m³). The contributions of the different stages to total PCN emissions decreased in the order feeding-fusion stage (65% of total PCN emissions) > oxidation stage (27%) > deoxidation stage (8%). The main contributor to PCN emissions during secondary copper smelting was the feeding-fusion stage. PCN concentrations and profiles in stack gas, fly ash, and deposit ash collected during different smelting stages were determined. PCNs in stack gases were mainly less-chlorinated homologs, and fly ash and deposit ash were dominated by highly-chlorinated homologs. These results will help improve strategies for decreasing and eliminating PCN emissions during secondary copper production.

Unintentional persistent organic pollutants in cement kilns co-processing solid wastes

Co-processing solid waste in cement kilns has become increasingly widespread in recent years. Persistent organic pollutants (POPs) can be unintentionally produced and emitted from cement kilns, especially kilns in which solid waste is co-processed. Unintentionally produced POP formation and emission by cement kilns co-processing solid waste therefore need to be studied in detail to allow the potential risks posed by cement kiln co-processing techniques to be assessed. Many field studies and laboratory simulation experiments have been performed to investigate the formation and release of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). However, the formations, characteristics and emission factors of various emerging unintentionally produced POPs have not been comprehensively reviewed. Here, emissions of well-known unintentionally produced POPs (PCDD/Fs and polychlorinated biphenyls) and emerging unintentionally produced dioxin-like POPs (polybrominated dibenzo-p-dioxins and dibenzofurans, polychlorinated naphthalenes, and chlorinated and brominated polycyclic aromatic hydrocarbons) in cement kilns co-processing solid waste are reviewed, focusing on formations and influencing factors of those unintentional POPs. Data from field studies indicated that the main stages in which POPs are unintentionally produced in cement kilns co-processing solid waste are the cyclone preheater outlet, suspension preheater boiler, humidifier tower, and back-end bag filter. The raw material composition, chlorine and bromine contents, and temperature are the most important factors affecting POP formation. The homolog distributions and congener profiles of POPs formed unintentionally in cement kilns were compared, and it was found that larger amounts of less-chlorinated homologs than more-chlorinated homologs are emitted. Emission factors for various unintentionally produced POPs for cement kilns co-processing solid waste were summarized, and could be useful for compiling global emission inventories for pollutants covered by the Stockholm Convention. This comprehensive review improves our understanding of unintentional production and emissions of POPs by cement kilns co-processing solid waste.